Pressure-driven magnetic moment collapse in the ground state of MnO

The zero temperature Mott transition region in antiferromagnetic, spin S = 52 MnO is probed using the correlated band theory LSDA + U method. The first transition encountered is an insulator–insulator volume collapse within the rocksalt structure that is characterized by an unexpected Hund’s rule violating ‘spin-flip’ moment collapse. This spin-flip to S = 12 takes fullest advantage of the anisotropy of the Coulomb repulsion, allowing gain in the kinetic energy (which increases with decreasing volume) while retaining a sizable amount of the magnetic exchange energy. While transition pressures vary with the interaction strength, the spin-flip state is robust over a range of interaction strengths and for both B1 and B8 structures. 4 Author to whom any correspondence should be addressed. New Journal of Physics 9 (2007) 235 PII: S1367-2630(07)44237-9 1367-2630/07/010235+12$30.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft